Textbook Question
How many signals would you expect to see in the 1H NMR spectrum of each of the following compounds?
g.
h.
1
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Ch. 14 - NMR Spectroscopy
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
Chapter 15, Problem 4m,n,o
How many signals would you expect to see in the 1H NMR spectrum of each of the following compounds?
m. 
n. 
o. 
Verified step by step guidance1
Step 1: Analyze the structure of the compound. The compound consists of a benzene ring and a carbon atom attached to three nitro groups (-NO2). The benzene ring is symmetric, and the substituent (C(NO2)3) is attached to one of its carbons.
Step 2: Determine the symmetry of the molecule. The benzene ring is symmetric, and the substituent does not disrupt this symmetry. This means that equivalent hydrogens on the benzene ring will give the same signal in the 1H NMR spectrum.
Step 3: Identify the unique hydrogen environments. In the benzene ring, there are two sets of equivalent hydrogens due to the symmetry: (a) two hydrogens ortho to the substituent, and (b) two hydrogens meta to the substituent. The para hydrogen is unique and forms a third environment.
Step 4: Count the number of signals. Since there are three unique hydrogen environments in the benzene ring, the 1H NMR spectrum will show three distinct signals.
Step 5: Consider splitting patterns and chemical shifts. The splitting patterns will depend on the coupling between hydrogens in adjacent environments, and the chemical shifts will be influenced by the electron-withdrawing effect of the nitro groups. However, the number of signals remains three.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nuclear Magnetic Resonance (NMR) Spectroscopy
NMR spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It relies on the magnetic properties of certain nuclei, primarily hydrogen (1H), to provide information about the number of distinct hydrogen environments in a molecule. Each unique hydrogen environment produces a separate signal in the NMR spectrum, allowing chemists to infer structural details.
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General NMR Features
Chemical Shifts
Chemical shifts in NMR spectroscopy refer to the variation in resonance frequency of nuclei due to their electronic environment. Different functional groups and molecular structures influence the electron density around hydrogen atoms, leading to shifts in their resonance signals. Understanding chemical shifts helps in predicting the number of signals and their positions in the spectrum, which is crucial for interpreting NMR data.
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Symmetry and Equivalent Protons
In organic molecules, symmetry can lead to equivalent protons, which are protons that experience the same electronic environment and thus produce a single NMR signal. Analyzing the symmetry of a compound helps in determining how many unique signals will appear in the NMR spectrum. For the nitro-substituted benzene compound shown, recognizing the symmetry and the effects of substituents is essential for predicting the number of signals.
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Related Practice
Textbook Question
How many signals would you expect to see in the 1H NMR spectrum of each of the following compounds?
a. CH3CH2CH2CH3
b. BrCH2CH2Br
3
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Textbook Question
If two signals differ by 1.5 ppm in a 300 MHz spectrometer, by how much do they differ in a 500 MHz spectrometer?
1
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Textbook Question
How many signals would you expect to see in the 1H NMR spectrum of each of the following compounds?
e.
f.
1
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Textbook Question
Draw an isomer of dichlorocyclopropane that gives an 1H NMR spectrum
c. with three signals
1
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Textbook Question
If two signals differ by 90 Hz in a 300 MHz spectrometer, by how much do they differ in a 500 MHz spectrometer